A student investigates how water availability affects the decomposition of dead mushroom tissue. Every container has the same mass of tissue, the same microbial inoculum and is left for 12 days.
| Container | Temperature / °C | Water added / cm³ | Air supply |
|---|---|---|---|
| P | 15 | 5 | air can enter |
| Q | 25 | 5 | air can enter |
| R | 25 | 15 | air can enter |
| S | 25 | 15 | air excluded |
Which pair of containers gives a valid test of the effect of water availability?
Containers P and Q
Containers R and S
Containers Q and R
Containers P and R
101 exam-style questions on Edexcel GCSE Biology 9.3 Material cycles and decomposition, covering 9.3.1 Cycling of materials through ecosystems, 9.3.2 The carbon cycle, 9.3.3 The water cycle, 9.3.4 The nitrogen cycle, 9.3.5 Indicator species and pollution, 9.3.6 Decomposition in preservation and composting, and 9.3.7 Rate changes in decay of biological material. Each one has a worked solution and a mark scheme showing where the marks go.